1. Field of the Invention
The present invention relates generally to graphical user interfaces and, more particularly, to hit-testing in a graphical user interface.
2. Related Art
Conventional signal measurement systems such as digital oscilloscopes sample, record and display time varying analog signals. Samples of an input signal are taken and quantized, and the resultant digital representations are stored in a waveform memory under the control of a sampling clock. The acquired data may subsequently be read out as locations in memory are sequentially addressed by a clock signal to provide digital data which can be converted to a time-varying output signal for a waveform display. The sampling clock may be operated at one of several selectable rates depending upon the frequency content of the input signal. The selection of the portion of the analog input signal which is sampled and stored is determined by appropriate triggering circuitry to enable the operator to display the desired portion of the waveform.
There are many types of display elements which can be presented in signal measurement systems in general and test and measurement instruments in particular. For example, in addition to the waveforms representing the signals currently received at the channel inputs, waveforms referred to as function waveforms may also be displayed. Function waveforms are waveforms created by processing the signal waveforms. Such processing may include, for example, performing arithmetic manipulations or combining multiple input signal waveforms in some predetermined manner. The resulting waveforms are placed in a display memory for subsequent retrieval and display. In addition, memory waveforms may also be displayed. Memory waveforms are waveforms which have been stored in memory for some predetermined time for later display. In addition to the above waveforms, other display elements such as marker indicators, trigger indicators, etc. are typically displayed.
Conventional test and measurement systems typically have numerous dials and knobs to control the many display elements which may be simultaneously visible on the display. However there is a limited amount of space to provide the large number of hardware controls. Accordingly, conventional test and measurement systems typically assign multiple functions to each control knob. This results in a complicated display panel which is often difficult to learn and use efficiently. To overcome this problem, some instruments have implemented what is commonly referred to as soft keys. Systems implementing soft keys provide a series of software-controlled function keys associated with physical buttons on the control panel. However, there are drawbacks to this approach as well. As the number of functions increases so too does the number of soft keys. Since the number of associated physical function keys adjacent to the soft keys is constant, as these additional functions are added to the system, a complicated multi-layered scheme of software-controlled functions is created. This hierarchy of soft keys is accessed through the limited number of physical keys on the instrument. A significant amount of time is required to navigate through the multiple layers to activate the desired function. In addition, the location of a desired function is not always intuitively associated with a higher level soft key and is therefore often difficult to locate.
What is needed, therefore, is a simple means for performing functions on display elements quickly and easily without having to perform a large number of control steps and operations.